Sheet to the tell tails as you are doing. You can add a few leech tell tails for fine tuneing the main. There is some additional tell tail placement info in the Hobie Forum FAQ. You trim the leech tails to alternate between flowing aft and hooking to the back side. Hooked all the time is over sheeted, flowing all the time is under sheeted.

Sounds like you can move the jib tack lower. Keep moving the tack lower on the forestay adjuster till you are nearly touching the car when sheeted as hard as you would for best performance.

Clew plate adjustment changes the leech and foot shape. Lower pulls more aft and opens the leech and tightens the foot. Higher pulls more down and tightens the leech. Adjust to match the shape of the main under sail. You have to duck under the boom and look at the slot between the sails. The curves should be similar for best flow.

Guys are moving the jib cars out further in higher wind going upwind.